The invention relates to an apparatus for strip processing with at least one uncoiling station, at least one strip processing station and at least one coiling station.
Such apparatus are known in a plurality of configurations. If the strip processing consists in trimming a strip, for example, the strip is uncoiled from a coil in an uncoiling station, fed to the trimming station, trimmed by a trimming knife in the trimming station and then coiled onto a coil by a coiling station. In addition to trimming, generic devices for strip processing are also used for parting, cold rolling or the like.
During the manufacture of a strip, this strip is generally subjected to a plurality of roll passes. Over the majority of the strip width, the reduction in thickness during rolling leads to an increase in the length of the strip. Near the strip edges however, in addition to the effect of increasing strip length during rolling, there is also an increase in strip width. As a result of the increase in the width of the strip at the strip edge, less material is available for the increase in the strip length at the strip edge which has the result that a more or less high strip-edge stress appears in the strip. The strip-edge stress described results in various problems during further processing of the strip. During the manufacture of can-body strip, for example, which is processed to form drink-can bodies in further processing steps, as a result of the generally very high strip-edge stress in this strip, undesirable edge lengthening occurs during trimming as a result of friction of the cut edges on the trimming knife. This undesirable edge lengthening leads, on the one hand, to a so-called starburst or star pattern formation on the coiled coil and, on the other hand, results in poor machinability during the further processing.
Occasionally during the further processing of so-called can-lid strip some strip cracking occurs during the stretching carried out during the further processing, which may have its origin, among other things, in the fact that the strip edges of the can-lid strip supplied for further processing have a high strip-edge stress and thus favour cracking during stretching.
Finally, a high strip-edge stress during the rolling process has the result that during each roll pass, a higher rolling energy must be applied to overcome the strip-edge stress than would be needed if this strip-edge stress were completely reduced. Thus, if the strip-edge stress can be reduced during two passes, the rolling energy required on the second pass is reduced.